A traditional human-machine interface, such as a command-line, menu-driven, or graphical user interface, receives user inputs via various channels, such as a mouse, a keyboard, and a touch-screen. However, this provides limitations in issuing commands to the interface, such as performing complex navigation, sorting and selection tasks. The use of spatial gestures has emerged to provide a natural and intuitive human-machine interaction under less constrained environments. A gesture is a natural body action that contains information (e.g., waving a hand to signify a greeting). Traditional spatial gesture-based interface systems respond to gestures in a spatial operating environment in an application. However, these systems detect and interpret both intentional and unintentional gestures as input commands to the application, thus misinterpreting random and unintended gestures as undesired input commands.
Furthermore, collaboration between users in one or more spatial operating environments to control common data or a common application via a device interface is not available. Normal human interaction between users during collaboration typically involves communication by words and by natural gestures (e.g., waving a hand to signify “good-bye”). However, it is difficult to distinguish a natural gesture used for communication between collaborating users from an intended gesture input since all gestures within the range of the sensing device are detected as user inputs. Therefore, natural gestures that are used for communication between collaborating users are less useful as intended gesture inputs. Instead, the intended gesture inputs are typically a collection of specific motions that must be memorized by the users, thus requiring significant effort on the part of the users to remember these gestures.